GB910223A - Improvements in or relating to fluid operable control devices - Google Patents

Abstract

910,223. Machinery safety devices. ROSS OPERATING VALVE CO. Oct. 21, 1960 [Nov. 20, 1959], No. 36274/60. Class 80 (4). [Also in Group XXIX] A device controlling fluid flow from two manually operable valves 13, 14 to a fluid receiver e.g. 16, comprises a safety valve 39 reciprocable between positions respectively permitting and preventing such flow, means responsive to the actuation of both manual valves at the same or nearly the same time for urging the safety valve towards its open position, and means responsive to the actuation of only one of the manual valves for urging the safety valve to its closed position. Simultaneous actuation of the valves 13, 14 allows air pressure to act past one or both of the ball valves 33, 34 separated by a spacer 32 so that air passes via passage 42 and acts on the lower surface of poppet 39 corresponding to cross-section of bore 39 to lift the poppet and pass at 44 to a fluidactuated valve 16 controlling flow and exhaust from a fluid motor 15. Poppet 39 is held open with a force greater than its opening force and corresponding to the pressure acting over the cross-section of larger bore 38 closed by the poppet. Pressure air from the valves 13, 14 also acts via passages 47, 48, and via one or both sides of shuttle ball valve 49, and via adjustable restriction member 58 to a capacity chamber 64 to build up the pressure within a predetermined time on a piston 65 abutting poppet valve 39. Poppet outlet pressure at 44 can also pass quickly to chamber 64 via check valve 68. However the pressure acting on piston 65 will not close poppet 39 since the force produced on piston 55 is either equal or slightly less than the force produced on poppet 39 when it abuts the end of bore 38. Should only one of the valves, e.g. 13, be opened then air pressure closes ball valve 33 on its seat preventing pressure from opening the poppet and passes via passage 47, valve 49 and restrictor 58 to build up pressure at a predetermined rate in chamber 64. After the predetermined time the force on piston 65 holds poppet 39 in its lower closed position over the small area seat 41. If the second valve 14 is operated within a predetermined time, e.g. before pressure has built up in chamber 64 to act on piston 65 and close poppet 39, pressure then acts past ball valve 34 and through passage 42 to act on the small lower area of poppet 39 whereby the valve 39 is lifted since the force on piston 65 has not reached its closing value. If valve 14 is actuated after the predetermined time, pressure beneath poppet 39 is prevented from opening it because of the larger downward force on the piston 65. With valves 13, 14 and 39 open, should one of the valves, e.g. 14, be closed, pressure beneath poppet 39 flows via passage 42, valve 34, passage 26 and valve 14 to exhaust whereby pressure in chamber 64 closes the poppet on seat 41 via piston 65 and pressure within chamber 64 is retained by ball valve 49 closing on seat 52. On closing valve 13 pressure in chamber 64 moves restrictor 58 away from its adjusting member 61 to flow unrestrictedly past ball valve 49 to exhaust through valve 13 and the apparatus is ready for further actuation by operation of both valves 13, 14. Outlet 44 may lead directly to the motor 15. Vent passage 71 allows valve 39 to close when seal head 73 of adjusting screw 62 is removed.